Approach to Hyponatremia

Hyponatremia is a common electrolyte abnormality in hospitalized children. When approaching a case of undifferentiated hyponatremia, it is important to determine whether it is true hyponatremia or a lab error. This can be done by repeating the serum sodium and measuring the serum osmolality. Differentiating between ADH-dependent and ADH-independent states is crucial. ADH-dependent causes involve inappropriate ADH secretion, which can be triggered by various conditions such as respiratory illness, surgery, pain, emesis, and anxiety. ADH-independent causes include primary polydipsia, renal failure, and conditions with low osmotic load like the toddler diet. Gathering a thorough history, assessing volume status, and monitoring urine osmolality are important steps in the diagnostic process.